There are numerous applications in which polyurethane foam is used at a site for any number of applications in addition to its traditional use in the building trades as a source of insulation. Recently polyurethane foam has become used with increasing frequency as a sealant in the building trades for sealing spaces between window and door frames and the like and as an adhesive for glueing flooring and roof tiles and the like. The polyurethane foam for such in situ applications is typically supplied as a one-component froth foam or a two-component froth foam. A one-component foam means that both the resin and isocyanate for the foam is supplied in a single pressurized container and dispensed from the container through a valve or gun attached to the container. A two-component "froth" foam means that one component is supplied in one pressurized container, typically the "A" container (i.e., polymeric isocyanate, fluorocarbons etc) while the resin is supplied in a second pressurized container, typically the "B" container (i.e., polyols, catalyst, flame retardants etc.). Typically two-component kits use pressurized cylinders about 71/2" in diameter which are connected by hoses to a dispensing gun. There are advantages and disadvantages to one-component and two-component foams. One of the advantages of the two-component system is its relatively long shelf life resulting from the fact that the chemicals are not mixed until they encounter one-another in the dispensing gun. This invention relates to two-component foams.
One particularly unique application for a hand-held, portable two-component polyurethane froth foam kit exists in the mining industry. In the event of a fire in a shaft being tunneled, standard procedure is to extinguish the fire by sealing the shaft with a fire "door" and then pumping out from the shaft sealed by the door, the air in the shaft to extinguish the fire. It has been found that polyurethane foam is excellent for sealing the bulkhead or door to the tunnel. As already noted, the polyurethane foam has an adhesive characteristic and the foam can be formulated to provide a relatively quick tack free time with little permeability for gas escape. Surprisingly, the fire door is not adjacent an open flame, and whatever temperature the gases exhausted from the shaft are, they are not sufficiently high in temperature to disintegrate the foam. Because of its long shelf life, a two-component foam is ideal for this application. Standard procedure is to simply provide two-component kits at the shaft being tunneled to seal and secure the fire door or bulkhead to the shaft in the event of a fire.
A two-component kit means the "A" and "B" cylinders, the dispensing gun and the hoses connecting the cylinders to the gun. Typically, these items are packaged in a cardboard container, box or carton and the carton is then used to hand carry the items to the site where the foam is to be dispensed. Because the cylinders are pressure vessels and contain chemicals that are deemed hazardous material, the carton must house the cylinders in such a manner that extensive safety regulations are complied with during shipping. One of the regulations require that the valve in the pressurized cylinders be shielded or guarded. See, for example, 49 C.F.R. subpart L, Sections 178.500 et seq. This regulation is typically complied with by providing a plastic or cardboard sheath or tube which fits over the valve stem protruding from the cylinder. When the kit is opened the sheath or tube is discarded and the hoses attached. Alternatively, the cylinder may be of a design where a sheet metal crown or guard is provided which surrounds or partially surrounds the valve stem. The crown typically has an opening for hand carrying the cylinder. Other regulations require the shipping carton to have sufficient strength and rigidity to permit stacking, dropping, etc.
A typical container for a two-component kit is a cardboard, fold-out box with a separate cardboard tray. The tray fits over the valved ends of the cylinders to hold the cylinders in place in the box during shipment and is integrated into the box such as by folding flaps fitting into tray slots at the box end adjacent the tray. The tray holds the cylinders and the box flaps hold the tray to the box. In the top of the tray, the hoses are placed in a coiled manner with the dispensing gun. To use, the operator opens the box end adjacent the tray and removes knock-out holes in the front face of the box. The hoses are then placed through the knock-out openings and tightened to the cylinder's valve fitting from above (discarding the protective shipping tubes) and the valves are opened. The cover is then folded back into the box to close the box and the hoses extend out of the box. Because the box end adjacent the tray has to be opened and closed to open and close the valves for use of the dispensing gun, the box is usually provided with a strap at the opposite box end which does not open. This means that the box is carried with the cylinders upside-down. However, this carton is perfectly acceptable for portable, hand-held, polyurethane froth foam in situ applications such as typically encountered in the building trades.
Different packaging arrangements are used by different manufacturers. Many two-component kit packages use some form of tray with knock-out holes through which the hoses extend after the box is opened and the hoses attached to the cylinder's valved fitting. However, there is at least one two-component polyurethane froth foam box which utilizes cylinders equipped with "dip tubes" which extend through the outlet valve from the inside bottom of the cylinder. This allows the cylinders to be placed upright in the box instead of upside down. This carton does not use a tray and has the hoses extend out the side of the box through knock-out plugs. The carton is carried by a strap affixed to the top cover. The top cover is a flap which has to be opened and closed to gain access to the cylinder's valve after the hoses are connected to the cylinders. While tests have not been conducted, the integrity of the carrying handle may be compromised if the box is constantly opened and closed.
In the mining application discussed, the two-component kits are simply left on the tunnel floor. The floor is moist and oftentimes wet. In time the moisture and/or water will weaken the cardboard corrugations rendering the box useless for carrying the two-component kit components to the site where the polyurethane foam is to be sprayed. Coating the box with a wax or plastic coating to make it more impervious to moisture significantly increases the cost of the carton and is not completely effective in preventing water from penetrating the cardboard corrugations. More importantly, when a fire occurs, there is little time to open a box, locate a wrench and tighten the hoses to the cylinders. On the other hand, if the kit is opened and the hoses attached, then the hoses and dispensing gun are permanently outside the box and exposed to the environment where damage can occur.